1. Field of the Invention
The present invention relates to a receiver and a receiving method for use in a wireless communication system. More particularly, the present invention relates to a channel estimating apparatus and method which takes into account neighbor sector or cell interference in a broadband multiple access wireless communication system.
2. Description of the Related Art
Communication systems were originally developed to provide voice services. Now, communication systems are being developed to provide packet data services and various multimedia services as well as voice services. An exemplary system capable of providing wireless packet data services is a third generation (3G) mobile communication system. The 3G mobile communication system provides various high speed multimedia services. The 3G mobile communication system distinguishes users using a Code Division Multiple Access (CDMA) scheme. The CDMA scheme distinguishes channels by allocating different orthogonal codes to users or to data transmitted to users.
However, the 3G mobile communication system fails to provide high speed data with high quality because of a lack of available codes. In other words, since the amount of usable codes are restricted, transmission rates are limited. To address this problem, researches and developers of mobile communication systems are considering a next-generation communication system which is referred to as the fourth generation (4G) broadband wireless communication system. The broadband wireless communication system is able to classify and transmit users or data to be sent, using an Orthogonal Frequency Division Multiple Access (OFDMA) scheme. The 4G wireless communication system features a high transmission rate of up to 100 Mbps. Furthermore, unlike the 3G system, the 4G system can provide services having various level of Quality of Service (QoS).
Currently, the 4 G communication system is being developed to guarantee mobility and QoS in a Broadband Wireless Access (BWA) communication system such as wireless Local Area Network (LAN) system and wireless Metropolitan Area Network (MAN) system. Exemplary communication systems include the Institute of Electrical and Electronics Engineers (IEEE) 802.16d communication system and the IEEE 802.16e communication system. However, various other systems using the OFDMA scheme are under development.
As discussed above, the broadband wireless communication system adopts the OFDMA scheme, ensures mobility, and utilizes the same frequency in every cell to increase frequency efficiency.
FIG. 1 is a simplified diagram of a conventional BWA system implemented with multiple cells.
In FIG. 1, Base Station (BS) 0, BS 1, and BS 2 are each communicating within their respective cells 100, 101 and 102 using the same frequency. In this situation, the multicell system has a frequency reutilization of ‘1,’ thereby increasing its frequency efficiency. However, by using the same frequency in adjacent cells, the resulting inter-cell or inter-sector interference may impair the performance of the system.
For example, in view of a Mobile Station (MS) 103 communicating with BS 0, a transmit signal of an MS 104 communicating with BS 1 of the neighboring cell and a transmit signal of an MS 105 communicating with BS 2 of the neighboring cell acts as interference signals to BS 0. In other words, BS 0 receives the interference signals 107 and 108 in addition to the received signal 106 from MS 103 in its cell. The interference signals of the neighboring cells affects the signal of MS 103 in the corresponding cell and thus deteriorates demodulation performance.
Therefore, a need exists for an apparatus and method for canceling interference caused by neighboring cells in a multicell system.